Document And Entity Information (USD $)	12 Months Ended
	Feb. 28, 2014	Mar. 31, 2014	Aug. 31, 2013
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Feb. 28, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Entity Registrant Name	CARMAX INC
Entity Central Index Key	0001170010
Entity Public Float			$ 10,621,543,601
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--02-28
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		220,805,697